Actuator Device

ABSTRACT

An actuator device for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed and the actuator including a motor-operated mandrel which is moved outwards in the actuator by means of a releasable nut, the nut being locked in its active position by means of a hydraulically operated locking piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of international application no. PCT/NO2008/000283, filed on Aug. 6, 2008, which claims the benefit of and priority to Norwegian application no. 20074140, filed on Aug. 9, 2007. The disclosures of the above-referenced applications are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to an actuator. More particularly, it relates to an actuator for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed. The actuator includes an actuator housing with an internal cylinder jacket and an end wall, there being arranged at the end wall a releasable nut which engages, in its active position, a threaded, axially bored-through mandrel, the mandrel projecting, axially movable, through an opening in the end wall. A motor is arranged to rotate the mandrel about its longitudinal axis via a non-circular, axially bored-through shaft. A locking piston, which is movable within the cylinder jacket, surrounds the mandrel, the locking piston being arranged to lock, when it is in its end position nearest to the end wall, the nut in its active position. An inner through opening in the wall of the shaft communicates with a first space in the actuator housing upstream relative to the locking piston when the mandrel is in its retracted position within the actuator housing, whereas an outer through opening in the wall of the mandrel communicates with a second space between the locking piston and the end wall when the mandrel is in its extended end position.

BACKGROUND

During work in a borehole, for example, the cleaning of a pipe, which is in the borehole, by means of a pressure-fluid tool which is on the end portion of a coiled tubing, it is well known that the feeding rate of the tool into the borehole may be irregular even though the coiled tubing is fed into the borehole at a regular rate.

The reason for this irregular rate of conveyance may be friction between the coiled tubing and borehole wall, obstructions in the borehole or curved boreholes, in which the coiled tubing changes the radius of curvature as it is being fed in. These conditions may result in a so-called “stick slip” effect, in which the tool stops, only to be moved, next, at a relatively high speed.

SUMMARY OF THE INVENTION

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art.

The object is achieved in accordance with the invention through the features which are specified in the description below and in the claims that follow.

An actuator in accordance with the invention for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed, is characterized by the actuator including an actuator housing with an internal cylinder jacket and an end wall, a releasable nut being arranged at the end wall, engaging, in its active position, a threaded, axially bored-through mandrel, the mandrel projecting, axially movable, through an opening in the end wall, and a motor being arranged to rotate the mandrel about its longitudinal axis via a non-circular, axially bored-through shaft, and a locking piston, movable in the cylinder jacket, surrounding the mandrel, the locking piston being arranged to lock, when it is in its end position nearest to the end wall, the nut in its active position, and an inner through opening in the wall of the shaft communicating with a first space in the actuator housing upstream relative to the locking piston when the mandrel is in its retracted position within the actuator housing, and an outer through opening in the wall of the mandrel communicating with a second space between the locking piston and the end wall when the mandrel is in its extended end position.

In its initial position the mandrel is in its retracted position, the locking piston is in an intermediate position between the piston and the nut, whereas the motor rotates the mandrel and thereby the tool about the longitudinal axis of the mandrel. Pressurized fluid flows through the axial bores of the shaft and mandrel.

Pressurized fluid flows via the inner opening into the first space, moving the locking piston up to the nut, where the locking piston causes the nut to be moved from its inactive position into its active position, engaging the threads of the mandrel.

The motor thereby feeds the mandrel out of its retracted position, whereby the liquid flow via the inner opening is shut off.

As the mandrel takes its projecting end position, the outer opening is uncovered, whereby pressurized fluid may flow into the second space. The locking piston is moved away from the nut which is thereby moved back into its inactive position.

With advantage, the mandrel is provided with a piston which is sealingly movable within the cylinder jacket. The fluid pressure moves the locking piston and the piston together with the mandrel in the direction of their initial positions. The further movement of the mandrel into its initial position may take place by means of, for example, a force directed at the actuator from the tool.

In an alternative embodiment the mandrel may be connected to a spring or gas spring which is arranged to move the mandrel in an inward direction within the actuator housing.

In a further embodiment the mandrel is moved inwards within the actuator housing by means of an external displacing force.

With advantage, the locking piston is provided with releasable locking dogs fitting complementarily into a locking groove in the cylinder jacket, the piston being provided with a releaser which is arranged to release the locking dogs when the piston is near the locking piston.

The motor is typically driven by means of pressurized fluid, but electric operation may also be applicable under certain conditions. It is advantageous that the motor is in the actuator housing, but the motor may also project, at least partially, from the actuator housing.

By the motor feeding the mandrel in a direction out of the actuator housing by means of a thread-nut-connection, a steady feeding rate is achieved, even if the axial force on the mandrel should vary somewhat. The device according to the invention provides a relatively simple actuator, in which the mandrel is moved automatically outwards at a constant rate, subsequently returning at a relatively high speed before the feeding out of the mandrel is repeated again.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows, is described an example of a preferred embodiment which is visualized in the accompanying drawings, in which:

FIG. 1 shows, partially in section, an actuator in accordance with the invention which is connected between a coiled tubing and a tool coupling;

FIG. 2 shows, on a somewhat larger scale, the actuator in its initial position;

FIG. 3 shows the same as FIG. 2, but here a locking piston is moving within the actuator;

FIG. 4 shows the actuator after the locking piston has moved the nut of the actuator into its active position;

FIG. 5 shows the mandrel of the actuator as it is being fed out;

FIG. 6 shows the actuator as the mandrel is in its projecting position;

FIG. 7 shows the actuator after the locking piston has been moved from its locking position relative to the nut; and

FIG. 8 shows a section III-III of FIG. 3.

DESCRIPTION OF THE INVENTION

In the drawings the reference numeral 1 indicates an actuator which is fitted between a coiled tubing 2 and a tool, not shown, by means of a tool holder 4.

The actuator 1 includes an actuator housing 6 which is provided with an internal cylinder jacket 8 and an end wall 10 at its end portion facing away from the coiled tubing 2. The end wall 10 is formed with a centric through opening 12. A pressure-fluid-operated motor 14 with a through centre opening 16 is connected to the actuator housing 6 and the coiled tubing 2 by means of an adapter 18.

Just inside the end wall 10 is arranged a nut housing 20 including a number of nut segments 22 pivotal in the nut housing 20. Each nut segment 22 is pivotal about a nut axle 24 between a passive position, see FIG. 2, and an active position, see FIG. 4. The nut segments 22 are held in their passive positions by an annular spring 26. Together the nut segments 22 constitute a nut 28.

In its active position the nut 28 is in engagement with a threaded, axially bored-through mandrel 30. The mandrel 30 projects, axially movable, through the opening 12 in the end wall 10, the mandrel 30 being connected to the tool holder 4.

At its opposite end portion, extending inwards, the mandrel 30 is provided with a piston 32 which is sealingly movable within the cylinder jacket 8. A through opening 34 of the mandrel 30, see FIG. 2, is along a portion of the opening 34 given a hexagonal shape, see FIG. 8, complementarily matching an axially bored-through shaft 36.

The shaft 36 is rotated about its longitudinal axis by the motor 14. An inner opening 40 through the wall of the shaft 36 corresponds with a bore 42 in the piston 32 when the mandrel 30 is in its retracted position, see FIG. 2. The mouth of the bore 42 is on the side of the piston 32 facing the nut 28.

A valve sleeve 44 is moved sealingly in over the inner opening 40 by means of a spring 46 as the mandrel 30 is moved away from its retracted position, see FIG. 5.

A locking piston 48 which is movable within the cylinder jacket 8 surrounds the mandrel 30. On its side facing the nut 28, the locking piston 48 is provided with an externally conical sleeve projection 50 which is arranged to be moved in under the portions 51 of the nut segments 22 facing the locking piston 48, the locking piston 48 thereby being arranged, when it is in its end position nearest to the end wall 10, to lock the nut 28 in its active position, in which the nut 28 is in engagement with the mandrel 30, see FIG. 4.

When the mandrel is in its projecting position, an outer opening 52 in the wall of the mandrel 30 is uncovered, the outer opening 52 then having its mouth between the end wall 10 and the locking piston 48.

In this preferred embodiment, the locking piston 48 is provided with a number of locking dogs 54 which are arranged to engage a locking groove 56 in the cylinder jacket 8, see FIG. 4. The piston 32 is provided with an axially movable, spring-biased release sleeve 58 which is biased in the direction of the end wall 10 by a spring 60. The release sleeve 58 is arranged to move the locking dogs 54 out of their respective engagements in the locking groove 56 when the piston 32 is at the locking piston 48, see FIG. 6.

In its initial position the mandrel 30 is in its retracted position, the locking piston 48 is in its intermediate position between the piston 32 and the nut 28. The motor 14 rotates the shaft 36, the mandrel 30 and thereby the tool, not shown, about the longitudinal axis 62 of the mandrel 30. Pressurized fluid from the coiled tubing 2 flows via the adapter 18, centre bore 16 of the motor 14, shaft 36 and mandrel 30 to the tool holder 4. At the same time, pressurized fluid is flowing via the inner opening 40 and the bore 42 of the piston 32 into a first space 64 between the piston 32 and the locking piston 48.

The locking piston 48 is moved in the direction of the nut 28 by the fluid pressure, see FIG. 3, until the locking piston 48 hits the nut 28, the sleeve projection 50 of the locking piston 48 being underneath the projecting portions 51 of the nut segments 22, whereby the nut segments 22 have been moved into their respective active positions, in which they are in engagement with the mandrel 30, see FIG. 4. At the same time, the locking dogs 54 engage the locking groove 56, thereby preventing the nut 28 from being movable inwards within the actuator housing 6.

The rotating mandrel 30, which is rotated by the motor 14, is screwed outwards within the actuator housing 16 by means of the nut 28, see FIG. 5. The spring 46 in the shaft 36 thereby moves the valve sleeve 44 closingly in over the second opening 40. Fluid from the first space 64 is evacuated via the bore 42 in the piston 32. Moreover, the actuator housing 6 can be replenished with fluid from the outside of the actuator 1 via an opening 66 in the actuator housing 6.

When the motor 14 has fed the mandrel 30 out into its projecting end position, see FIG. 6, the release sleeve 58 is underneath the locking dogs 54, whereby the locking dogs 54 have been pivoted out of their engagement with the locking groove 56. At the same time, the outer opening 52 communicates with a second space 68 located between the end wall 10 and the locking piston 48. In this preferred embodiment the nut 28 has been fed out of engagement from the mandrel 30 as well.

The pressure from the pressurized fluid flowing into the second space 68 works against the locking piston 48 and the force overcomes the force from the spring 60, whereby the release sleeve 50 is moved sufficiently far back relative to the piston 32 for the sleeve projection 50 of the locking piston 48 to be disengaged from the nut segments 22, see FIG. 7. The annular spring 26 moves the nut segments 22 into their respective inactive positions, whereby the mandrel 30 can be moved back into its retracted initial position.

In the figures are shown a number of seals which have generally been assigned the reference numeral 70. The purpose and operation of the seals 70 are well known and not described any further. Because of the relatively great flow rate of pressurized fluid prevailing, no great demands are made on the seals 70. For example, it has turned out to be unnecessary to place a seal between the end wall 10 and the mandrel 30. 

1. An actuator for moving a tool within a borehole in the ground, the actuator positionable between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed, the actuator comprising: an actuator housing with an internal cylinder jacket and an end wall; a releasable nut being arranged at the end wall, engaging, in its active position, a threaded bored-through mandrel, the mandrel projecting, axially movable, through an opening in the end wall; a motor being arranged to rotate the mandrel about its longitudinal axis via a non-circular, axially bored-through shaft a locking piston, movable in the cylinder jacket, surrounding the mandrel, the locking piston being arranged to lock, when it is in its end position nearest to the end wall, the nut in its active position; an inner through opening defined in the wall of the shaft communicating with a first space defined in the actuator housing upstream relative to the locking piston when the mandrel is in its retracted position within the actuator housing; and an outer through opening defined in the wall of the mandrel, communicating with a second space defined between the locking piston and the end wall when the mandrel is in its extended end position.
 2. The actuator of claim 1 wherein the locking piston includes releasable locking dogs fitting complementarily into a locking groove in the cylinder jacket, a second piston being provided with a releaser which is arranged to release the locking dogs when the second piston is near the locking piston.
 3. The actuator of claim 1 wherein the mandrel includes a second piston which is sealingly movable within the cylinder jacket, whereby fluid flowing through the outer through opening is arranged to move the second piston and mandrel in the inward direction within the actuator housing.
 4. The actuator of claim 1 wherein the mandrel is connected to a spring which is arranged to move the mandrel inwards within the actuator housing.
 5. The actuator of claim 1 wherein the mandrel is connected to a gas spring which is arranged to move the mandrel inwards within the actuator housing.
 6. The actuator of claim 1 wherein the motor is pressure-fluid-operated.
 7. The actuator of claim 1 wherein the motor is in the actuator housing.
 8. The actuator of claim 1 wherein the motor is at least partially outside the actuator housing.
 9. The actuator of claim 2 wherein the mandrel includes the second piston which is sealingly movable within the cylinder jacket, whereby fluid flowing through the outer through opening is arranged to move the second piston and mandrel in the inward direction within the actuator housing. 